Telemeter type hydraulic power transmitting system



April 15,1958 0. E. nuns-mom 2,830,561

TELEMETER TYPE HYDRAUL IC POWER TRANSMITTING SYSTEM Filed March 21, 19563 Sheets-Sheet 1 Indezzior aiSZrom m m @m o y WNW QWN NW Nm 1 r M 9 ap &a A 1 I- 0 \1i H hI lilw l m I'll-[III Ill- 4 mm a April 15, 1958 o. E.LINDSTROM 3 TELEMETER TYPE HYDRAULIC POWER TRANSMITTING SYSTEM In de 77for 050a?" E lISZ WdTZTOWZ PM@- M A ril 15, 1958 o. E. LINDSTROM2,830,561

TELEMETER TYPE HYDRAULIC POWER 'I'RAIISMI'ITING SYSTEM R) Q rzv'nior 0,5arELz'ndairom United States Patent Q 'IELEMETER TYPE HYDRAULIC POWERTRAN S- MITTING SYSTEM Oscar E. Lindstrom, St-Dizier, France, assignorto International Harvester Company, a corporation of New Jersey Thisinvention relates to a control mechanism for an hydraulic motor. More inparticular this invention relates to a new and novel control valve whichis adapted for a telemeter type control of an hydraulic powertransmitting system.

Heretofore in hydraulic control systems of this type a separate andcostly servo-motor has been employed to return the control means to aneutral position when the main hydraulic motor has reached apredetermined position corresponding to the position of the controllever as set by the operator. The movement of the servo-motor wasdetermined by the metering of fluid therethrough. Furthermore when suchcontrol means was in a neutral position excessive fluid pressure wouldbe required in the by-passing of fluid to the pump reservoir. inaddition these systems do not provide for hydraulically locking themotor from movement when the control means is in a neutral position orupon failure of the source of fluid flow.

It is therefore an object of this invention to provide a compact controlvalve mechanism adapted to a telemeter type hydraulic power transmittingcircuit.

A further object of this invention is to provide a telemeter typecontrol valve mechanism having a unique by-pass valve which is actuatedfor closing or opening by fluid pressure.

A still further object of this invention is to provide a telemeter typecontrol valve mechanism having an hydraulic locking means for preventingmovement of the motor under a load when the control valve mechanism isin a neutral position.

Still another object of this invention is to provide a telemeter typecontrol valve mechanism according. to the preceding object wherein thehydraulic locking means is releasable by the direct action of theby-pass valve mechanism.

These and other desirable objects and advantages of the invention willbecome apparent from the following description of a preferredembodiment, the appended claims and the drawings wherein:

Figure l is a side elevation, partly in section, illustrating theinvention where the control valve is in a neutral position.

Figure 2 is a side elevation, partly in section, similar to Figure 1except that the control valve is illustrated in an operating positionwhereby the hydraulic motor is moving in one direction.

Figure 3 is an enlarged side elevation, in section, of the control valveillustrating an intermediate stage of the valve mechanism which occursat the moment when the control valve is moved from a neutral position toan operating position.

Figure 4 is a side elevation, partly in section, similai to Figure 2except that the control valve is illustrated in an operating positionwhereby the hydraulic motor is moving in the other direction.

With reference to the drawings the numeral general- 1y indicates anhydraulic power transmitting system. The system 10 includes a controlvalve generally indicated at 11, a source of fluid flow which may be apump generally indicated at 12, a control lever indicated at 13, anhydraulic motor 14 having a movable work member 15, link means generallyindicated at 16 which interconnects the control lever 13 with the workmember 15 and control valve 11, a fluid return reservoir 17 and a safetyvalve 18 all connected together as generally shown in Figures 1, 2 and4.

The hydraulic motor 1 3 selected for illustration in this embodiment ofthe invention is an ordinary two-way hydraulic ram. The ram 14 iscomprised of the usual casing 19, piston 20, rear head member 21 havingan integrally connected mounting lug 22, a front head member 23 and aconnecting rod 24 rigidly connected at one end to the piston 2d andhaving lug member 25 at the other end thereof adapted for connection toa work load (not shown). Thus it may be seen that the assembly of thepiston 29 with the rod 24- and lug 25 constitute the movable work member15 of the motor The motor 14 is provided with the usual front cylinderchamber 26 and associated tube 2? for conducting fluid to and from thechamber 26. Likewise the motor 14 is provided with the usual rearcylinder chamber 28 and associated tube 29 for conducting fluid to andfrom the chamber 28. Thus by introducing fluid pressure into one of thetubes 27 or 29 while exhausting the other tube 29 or 27 causes the workmember 15 to be urged in the corresponding direction.

The source of fluid flow 12 may be an ordinary constant delivery typepump. The reservoir 17 is of the usual type associated with the inletside of the pump 12. Of course if the fluid selected is air thereservoir 17 may be omitted as the atmosphere then becomes the systemsreservoir. The safety valve 18 is of the well known type which bleedsfluid from the delivery side of the pump l2 when the system is subjectedto a fluid pressure exceeding a predetermined maximum limit therebypreventing damage to any of the components in the system.

The control valve 11 which forms the main feature of this invention iscomprised, among other things, of a housing 353 which housing may, formanufacturing reasons, consist of a plurality of parts or sectionsassembled together rigidiy by any well known means such as bolts and thelike. The upper portion of the housing 36' is provided with a first bore31 extending longitudinally through the rear wall of the housing 3i). Aniniet port 32 is disposed in the upper portion of the housing 30 and influid communication with the bore 31 and pipe 33 leading to the outletof the pump 12. A first service port 34 is dis posed rearwardly of theinlet port 32 in the housing 30 which port communicates for fluid flowthe bore 32 with the tube 29 of the motor 14. A second service port 34'is disposed forwardly of the inlet port 33 in the housing 30 which portcommunicates for fluid flow the bore 31. with the tube 27 of the motor14.

On the forward end of the bore 31 in the housing 34! is a discharge port35 connecting the bore 31 with the reservoir 17 through a pipe 3-6.

The bore 31 is provided with a main valve plunger generally indicated at37. Th plunger 37 is slidably fitted into the bore 31 for axial movementtherein and extends through the rearward opening of the bore 3! in thehousing 39 so that the rearward portion of the plunger 37 protrudesexternally of the housing 3i as shown in each of the drawings. Theplunger 37 is provided with a first land 38 which is positioned inregisterable reiation with the opening of the first service port 34 intothe bore 3-1. Forwardly of the first land 38 on the plunger 37 is asecond land 33 which is spaced from the first land 38 such that when thefirst land 38 is in registry with the first service port 34 the secondland 38' will also be in registry with the second service port 34'.Between the first and second lands 38 and 38 on the plunger 37 is alarge circumferential groove 39 which groove is continuously inregistration with the inlet port 32 throughout the range of axialmovement of the plunger 37. Rearwardly of, and adjacent to, the firstland 38 on the plunger 37 is a small circumferential groove 40 whichgroove is regisetrable with the first service port 34. A fluid passagebetween the small circumferential groove 4%) and the forward end portionof the bore 31 leading into the discharge port 35 is provided by anaxially disposed recess 41 in the plunger 37 extending from the forwardend of the plunger 37 and connected with the groove 40 by a transversehole 41' as best shown in Figure 3. Thus the small circumferentialgroove 40 is in continuous fluid communication with the discharge port35.

The control valve 11 is also provided with a second bore 42 disposed inthe housing 30. Centrally located and communicating for fluid flow thebore 42 with the inlet port 32 is a by-pass conduit 43. Formanufacturing convenience the by-pass conduit 43 may communicate withthe inlet port 32 by opening into the bore 31 in alinement with port 32as shown in each of the drawings. Since the large circumferential groove39 is always in registration with the inlet port 32 and the by-passconduit 43 fiuid communication between the conduit 43 and the inlet port32 is continuously established.

Into the second bore 42 is slidably fitted a pair of movable elements 44and 44 in opposed relation. The inner faces of the elements 44 and 44may be beveled to facilitate the separation of the two elements fromeach other which will be hereinafter explained. On the outer ends ofeach of the elements 44 and 44' are captive springs 45 and 45',respectively, adapted to urge the elements 44 and 44 inwardly or towardeach other.

Opening into the bore 42 positioned in alinement with the by-passconduit 43 is a discharge conduit 46 which communicates for fluid flowthe bore 42 with the discharge port 35 as shown partly in dotted lineson Figure 3.

It will be seen from the drawings that rearward of the movable element44 in the bore 42 is formed a first by-pass chamber 47. Opening into thefirst bore 31 and in fluid communication with the first lay-pass chamber47 is a first by-pass actuating port 48. Now referring to Figure 1 itwill be noted that the actuating port 48 is slightly offset rearwardlyfrom direct alinmement with the first service port 34. Thus when thefirst land 38 of the plunger 37 is in complete registration with thefirst service port 34 the actuating port 48 is in fluid communicationwith the small circumferential groove 40 for a purpose to be describedlater. Again from the drawings it will be seen that forward of themovable element 44 in the bore 42 is formed a second by-pass chamber 47.Opening into the bore 31 and in fluid communication with the secondby-pass chamber 47 is a second by-pass actuating port 48'. Now againfrom Figure 1 it will be noted that the second actuating port 48 isslightly oflset forwardly from direct alinement with the second serviceport 34'. Thus when the second land 38' of the plunger 37 is in completeregistration with the second service port 34' the second actuating port48 is in fluid communication with the forward end portion of the bore 31and discharge port 35 for a purpose to be described later.

interposed in the first service port 34 between the first bore 31 andthe tube 29 in the housing 30 is disposed at first check valvevgenerally indicated at 49. The check valve 49 may conveniently be formedby a recessed portion St in the housing 30 connected or interposedserially with the first service port 34. Into the recessed portion Stlis slidably fitted the well known valve closing element 51 adapted toseat against the housing 30 in the usual manner. A small captive spring52 is disposed in the recessed portion 50 and is adapted to urge theclosing element 51 in seating relation with the housing 30. It will benoted from the drawings that the check valve 49 is disposed in seriesrelation with the first service port 34 and is openable in response tofluid flow in one direction emanating from the bore 31. In the housing30 in axial alinement with the recessed portion 50 is hole 53 which holeslidably supports a drive pin 54. The drive pin 54 may, but notnecessarily, be made integral with the closing element 51 and extendsforwardly into the first by-pass chamber 47.

interposed in the second service port 34' between the first bore 31 andthe tube 27 is disposed in the housing 30 a second check valve generallyindicated at 49. The check valve 49 may conveniently be formed by arecessed portion 50 in the housing 30 connected or interposed seriallywith the second service port 34'. Into the recessed portion 50' isslidably fitted the well known valve closing element 51' adapted-to seatagainst the housing 30 in the usual manner. A small captive spring 52'is disposed in the recessed portion 50 and is adapted to urge theclosing element 51 in seating relation with the housing 30. Again itwill be noted from the drawings that the check valve 49 is disposed inseries relation with the second service port 34 and is openable inresponse to fluid flow in one direction emanating from the bore 31. Inthe housing 30 in axial alinernent with the recessed portion 50' is hole53' which hole slidably supports a drive pin 54. Again, as before, thedrive pin 54' may, but not necessarily, be made integral with theclosing element 51 and extends rearwardly into the second bypass chamber47.

The control lever 13 is comprised of a manually operable handle 55pivotally mounted at 56. A portion 57 of the handle 55 extends below thepivot 56 and is provided with an elongated aperture 58. The link means16 for interconnecting the control lever 13 with the valve plunger 37and the movable work member 15 of the motor 14 may be comprised of abeam 59 pivotally connected at 60 to one end of a rod member 61. Theupper end of the beam 59 is pivotally connected to the handle 55 at 62through the elongated aperture 58. From this it can be seen that theelongated aperture provides the necessary take-up allowance during thearcuate travel of the pivot 62. The rearward end portion of the plunger37 is pivotally connected at 63 to the beam 59 and the other end of therod member 61 is pivotally connected at 64 to the movable work member15' of the motor 14.

Operation From the drawings it will readily be seen that the movingparts within the second bore 42 comprise a bypass valve while the valveplunger 37 in the first bore 31 comprises the main valve portion of thecontrol valve 11. Figure 1 illustrates the control valve 11 in a neutralposition. Fluid enters the control valve 11 from pipe 33 into the inletport 32 and thence into the large circumferential groove 39. The firstand second lands 38 and 38 are in respective registration with the firstand second service ports 34 and 34'. Thus no fluid flows into either ofthe tubes 27 or 29 to energize the motor 14. Fluid in the first by-passchamber 47 may exhaust through the first by-pass actuating port 48 pastthe rear edge of the first land 38 into the small circumferential groove4-0 thence through the hole 41' into the axially disposed recess 41 intothe forward end portion of the bore 31 and out the discharge port 35into the pipe 36 leading to the reservoir 17. Likewise fluid in thesecond by-p'ass chamber 47' may exhaust through the second by-passactuating port 48 past the forward edge of the second land 38' into theforward end portion of the bore 31 and out the discharge port 35 intothe pipe 36 leading to the reservoir 17. From this it can be seen thatwhen the plunger 37 is in a neutral position there exists no fluidpressure differential between the first and second by-pass chambers 47and 47'. Furthermore the exhausting of fluid from the chambers 4-7 and47 is unrestricted.

While the control valve 11 is in a neutral position the fluid enteringthe inlet port 32 from the pump 12 flows into the by-pass conduit 43 andthe pressure thereof acts on the bevelled surfaces on the inner faces ofthe movable elements 44 and 4-4 to move the element 44 rearwardlyagainst the urging of the spring 52 and move forwardly the element 44'against the urging of spring 52. Thus the elements 44 and 44' areseparated by respective axial movement resulting in an openingcommunicating the bypass conduit 43 with the discharge conduit 46. Fromthis it can be seen that the fluid flow from the pump 12 entering theinlet port 32 flows into the by-pass conduit 43 and thence between theseparated elements 44 and 44 into the discharge conduit 46 to thedischarge port 35, thence into the pipe 36 to the reservoir 17 and backto the pump 12 through the pipe 65. Thus when the control valve 22 is ina neutral position the pump operates at a relatively low pressure, thefluid being by-passed back to the reservoir 17.

When the control valve 11 is in a neutral position both first and secondcheck valves 49 and 4-3 are in closed position which prevents theexhaust of fluid in the cylinder chambers 26 and 28 and the associatedtubes 27 and 29 of the motor 14 thus hydraulically locking the positionof the motor 14. At this point it should be noted that the motor 14 willremain hydraulically locked in the event of failure of the pump 12 eventhough the plunger 37 is moved from the neutral position toan operatingposition. This safety feature will become more evident from the ensuingdiscussion.

Now suppose the operator moves the control lever 13 forwardly from thatshown in Figure 1 to, for example, that position shown in Figure 4.Since the work member 15 is momentarily stationary the rod member 61will also be stationary. Thus, the movement of the control lever 13causes the beam 59 of the link means 16 to pivot about the point 60. Asa consequence of the movement of the beam 59 the valve plunger 37 iscaused to move rearwardly to a position illustrated in Figure 4.Immediately upon the movement of the valve plunger 37 from a neutralposition shown in Figure l to an operating position shown in Figure 4the by-pass valve and check valves 49 and 49' shift to the positionshown in Figure 4. However, the intermediate stage during this shift isillustrated in Figure 3.

From Figure 3 it will be seen from the position of the plunger 37 thatfluid flow from the pump 12 entering the inlet port 32 is now permitedto enter the first service port 34 and the first by-pass actuating port48 because the first land 38 has moved rearwardly thus registering thelarge circumferential groove 33 with both ports 34 and 48. From this itis seen that a rise in fluid pressure occurs in the first by-passchamber 47. At the same time the second by-pass chamber 47 may stillexhaust fluid into the forward end portion of the bore 31 and out thedischarge port 35 to the reservoir 17 through the pine 36. Thus apressure differential exists between the first and second by-passchambers 47 and 47' which pressure differential acts on the rear end ofthe movable element 44 urging it in a forward direction. As the element44 moves forwardly the flow of fluid through the by-pass conduit 43becomes restricted which results in a further pressure rise in the fluidfrom the pump 12 at the inlet port 32. This .rise in fluid pressurecontinues to move the element 44 in "a forward direction to terminatefluid flow in the conduits 43 and 46 and, in addition, abuts the element44' whereby both elements 44 and 44 move forwardly. The continuedforward movement of the elements 44 and 44' causes the forward end ofthe element 44' to engage the drive pin 54' and moving the pin 54forwardly to unseat or open the second check valve 49'. Now as thebypassing of fluid through the conduit 43 diminishes, the fluid pressureat the inlet port 32 increases to a point where it is suflicient tounseat or open the first check valve 49 thus allowing fluid flow throughthe service port 34 to the tube 29 into the rear cylinder chamber 28 ofthe motor 14. Thus fluid communication from the inlet port 32 to therear cylinder chamber 28 is established to urge movement of the workmember 15 of the motor 14 in a forward direction. The exhaust fluid fromthe front cylinder chamber 26 of the motor 14 passes through the tube 27into the second service port 34 in reverse direction through the opensecond check valve 49 into the forward portion of the bore 31 and outthrough the discharge port 35 and pipe 36 to the reservoir 17. At thispoint the control valve mechanism 11 has shifted completely from theneutral position of Figure 1 to the operating position of Figure 4.

As the work member 15 of the motor 14 proceeds forwardly with the rodmember 61, the beam 59 is caused to move pivotally about the point 62which in turn moves valve plunger 37 forwardly until the plunger 37again reaches a neutral position whereupon the motor 14 again becomeshydraulically locked and the control valve 11 reestablishes a fluidby-pass as shown in Figure l. The hydraulic locking of the motor 14occurs at the time when the lands 38 and 33' register completely withthe respective openings of service ports 34 and 34 into the bore 31thereby preventing fluid flow to and from the motor 14. Fluid pressurepreviously existing in the chamber 47 is then discharged through theby-pass actuating port 48 to the small circumferential groove 4% intothe hole 41 thence through the axially disposed recess 41 into theforward portion of the bore 31 and out to the reservoir 17 through thedischarge port 35 and pipe 36. Thereafter the movable elements 44 and 44of the by-pass valve move to a central position in the bore 42 at theurging of the springs 45 and 45. The fluid pressure at the inlet port 32and by-pass conduit 43 then acts on the bevelled edges on the innersurfaces of the movable elements 44 and 44' causing the separationthereof to re-establish fluid by-pass therebetween as previouslyexplained.

Now suppose the handle 55 of the control lever 13 is moved by theoperator rearwardly from the position shown in Figure l to a position,for example, shown in Figure 2. Since the work member 15 is momentarilystationary the rod member 61 will also be stationary. Thus the movementof the control lever 13 causes the beam 59 of the link means 16 to pivotabout the point 60. As a consequence of the movement of the beam 59 thevalve plunger 37 is caused to move forwardly to a position illustratedin Figure 2. Immediately upon the movement of the valve plunger 37 froma neutral position shown in Figure l to an operating position shown inFigure 2 the by-pass valve and check valves 49 and 49' shift to theposition shown in Figure 2. Fluid flow from the pump 12 entering theinlet port 32 is now permitted to enter the second service port 34' andthe second by-pass actuating port 48' because the second land 38' hasmoved forwardly thus registering the large circumferential groove 39with both ports 34 and 48. From this it is seen that a rise in fluidpressure occurs in the second by-pass chamber 4-7. At the same time thefirst by-pass chamber 47 may still exhaust fluid to the smallcircumferential groove 40 into the hole 41 and axial recess 41 to theforward end portion of the bore 31 and thence out the discharge port 35to the reservoir 17 through the pipe 36. Thus a pressure differentialexists between the first and second by-pass chambers 47 and 47 whichpressure differential acts on the forward end of the movable element 44'in a rearward direction. As the element 44' moves rearwardly the flow offluid through the by-pass conduit 43 becomes restricted which results ina further pressure rise in the fluid from the pump 12 at the inlet port32. This rise in fluid pressure continues to move the element 44' in arearward di ection to terminate flow of fluid in the conduits 43 and 46and, in addition, abuts the element 44 Whereby both elements 44 and 44'move rearwardly. The continued rearward movement of the elements 44 and44 causes the rearward end of the element 44 to engage the drive pin 54and moving the pin 54 rearwardly to unseat the first check valve 49. Nowas the by-passing of fluid through the conduit 43 diminishes, the fluidpressure at the inlet port 32 increases to a point where it issuflicient to unseat the second check valve 49' thus allowing fluid flowthrough the service port 34 to the tube 27 into the front cylinderchamber 26 of the motor 14. Thus fluid communication from the inlet port32 to the front cylinder chamber 26 is established to urge movement ofthe work member 15 in a rearward direction. The exhaust fluid from therear cylinder chamber 28 of the motor 14 passes through the tube 29 intothe first service port 34 in reverse direction through the open firstcheck valve 49 to the small circumferential groove 40 into the hole 41'and axial recess 41 to the forward portion of the bore 31 and outthrough the discharge port 35 and pipe 36 to the reservoir 17. At thispoint the control valve mechanism 11 has shifted to the operatingposition of Figure 2.

As the work member 15 of the motor 14 proceeds rearwardly with the rodmember 61, the beam 59 is caused to move pivotally about the point 62which in turn moves the valve plunger 37 rearwardly until the plunger 37again reaches a neutral position whereupon the motor 14 again becomeshydraulically locked and the control valve 11 reestablishes a fluidby-pass as shown in Figure 1 in a similar manner as that described foroperation in the opposite direction.

From the above it can be seen that the work member 15 of the motor 14will always be urged by fluid flow through the control valve 11 to aposition in its stroke corresponding to the relative position of thestroke of the control lever 13 and when the member reaches such positionthe motor 14 becomes hydraulically locked from (further movement ineither direction. Furthermore in the event of failure of the pump 12 themovement of the plunger 37 will not release the check valves 49 and 49'to open the hydraulic lock of the motor 14 thus preventing accidentaldamage to the load on the motor 14 such as the dropping of a plow intransport position on a tractor to the ground.

Having thus described an embodiment of the invention, it can now be seenthat the objects of the invention have been fully achieved and it mustbe understood that changes and modifications may be made which do notdepart from the spirit of the invention nor from the scope thereof asdefined in the appended claims.

What is claimed is:

1. A control valve for an hydraulic system comprising a housing havingan inlet port and a discharge port, a first bore disposed in saidhousing, one end of said first bore extending through an external wallof said housing, a first service port and a second service port disposedin said housing, said service ports being communicatively connected forfluid flow with said first bore, a movable main valve plunger slidablydisposed in said first bore, one end of said'valve plunger protrudingexternally of said housing, a first land and a second land disposed onon said valve plunger, said first land being positioned to register withsaid first service port when said second land is in registration withsaid second service port, a large circumferential groove disposed onsaid valve plunger, said large circumferential groove being positionedbetween said lands and in continuous registration with said inlet port,a small circumferential groove disposed on one end portion of said valveplunger adjacent said first land and registerablewith said first serviceport, a fluid passage disposed in said valve plunger, said passagecommunicatively connecting for fluid flow said small circumferentialgroove with said discharge port, a first check valve disposed in saidhousing, said first check valve being interposed in and connected inseries relation with said first service port, a second check valvedisposed in said housing, said second check valve being interposed inand connected in series relation with said second service port, saidcheck valves being openable responsive to fluid pressure in onedirection, said check valves each being provided with a drive pin, saiddrive pins being movable for selectively opening said check valves forpermitting fluid flow therethrough in the other direction, a second boredisposed in said housing, a first by-pass actuating port and a secondby-pass actuating port disposed in said housing communicativelyconnecting for fluid flow said first bore with said second bore, a fluidpressure actuated by-pass valve disposed in said second bore, a by-passconduit communicatively connecting for fluid flow said inlet port withsaid second bore, a discharge conduit disposed in said housingcommunicatively connecting for fluid flow said second bore with saiddischarge port, said by-pass valve having a pair of movable valveelements slidably disposed in said second bore, resilient means disposedon the outer ends of said movable elements positioned for urging saidmovable elements toward each other in opposed relation, the outer end ofone of said movable elements being positioned to engage the drive pin ofsaid first check valve and the outer end of the other of said movableelements being positioned to engage the drive pin of said second checkvalve, said control valve being operable to by-pass fluid flow from saidinlet port through said by-pass valve while said check valveshydraulically lock the movement of fluid in said service ports andalternatively connecting for fluid flow said inlet port with one of saidservice ports and connecting for fluid flow said discharge port with theother of said service ports while terminating fluid flow from said inletport through said by-pass valve to said discharge port.

2. An hydraulic power transmitting system comprising a source of fluidflow, a two-way acting fluid motor including a movable work member, acontrol valve, said control valve having a housing, an inlet portdisposed in said housing, said inlet port being communicativelyconnected for flu-id flow with said source of fluid flow, a dischargeport disposed in said housing, said discharge port being communicativelyconnected for fluid flow with the fluid supply for said source of fluidflow, a first service port and a second service port disposed in saidhousing, said service ports being communicatively connected to saidmotor for energizing said motor when said control valve is in anoperating position, a first bore disposed in said housing, one end ofsaid first bore extending through an external wall of said housing, amovable main valve plunger slidably disposed in said first bore, one endof said valve plunger protruding externally of said housing, a firstland and a second land disposed on said valve plunger, said first landbeing positioned to register with said first service port when saidsecond land is in registration with said second service port, a largecircumferential groove disposed on said valve plunger, said largecircumferential groove being positioned between said lands and incontinuous registration with said inlet port, a small circumferentialgroove disposed on one end portion of said valve plunger adjacent saidfirst land and registerable with said first service port, a fluidpassage disposed in said valve plunger, said passage communicativelyconnecting for fluid flow said small circumferential groove with saiddischarge port, a first check valve disposed in said housing, said firstcheck valve being interposed in and connected in series relation withsaid first service port, a

second check valve disposed in said housing, said second check valvebeing interposed in and connected in series relation with said secondservice port, said check valves being openable responsive to fluidpressure in one direction, said check valves each being provided with adrive pin, said drive pins being movable for selectively opening saidcheck valves for permitting fluid flow therethrough in the otherdirection, a second bore disposed in said housing, a first by-passactuating port and a second by-pass actuating port disposed in saidhousing, said first by-pass 9 port being poitioned to communicate forfluid flow one end portion of said first bore with one end portion ofsaid second bore, said first by-pass actuating port being positioned forselective registration with said first land and said circumferentialgrooves, said second by-pass actuating port being positioned tocommunicate for fluid flow the other end portion of said first bore withthe other end portion of said second bore, said second by-pass actuatingport being positioned for selective registration with said second landand said large circumferential groove and said discharge port, a fluidpressure actuated by-pass valve disposed in said second bore, a by-passconduit communicatively connecting rfor fluid flow said inlet port withsaid second bore, a discharge conduit disposed in said housingcommunicatively connecting for fluid flow said second bore with saiddischarge port, said by-pass valve having a pair of movable elementsslidably disposed in said second bore, one of said movable elementsforming a first by-pass chamber with one end portion of said second boreand the other of said movable elements forming a second by-pass chamberwith the other end portion of said second bore, said first by-passactuating port being in communication with said first by-pass chamberand said second by-pass actuating port being in communication with saidsecond by-pass chamber, resilient means disposed on the outer ends ofsaid movable elements positioned for urging said movable elements towardeach other in opposed relation, the outer end of one of said movableelements being positioned to engage the drive pin of said first checkvalve and the outer end or the other of said movable elements beingpositioned to engage the drive pin of the said second check valve, saidmovable elements being position to separate from each other responsiveto fluid pressure differential between said by-pass conduit and saiddischarge conduit for fluid flow therethrough, means for selectivelyconnecting one of said by-pass chambers with said inlet port andconnecting the other of said by-pass chambers with said discharge portfor terminating flow of fluid through said by-pass conduit when saidvalve plunger is in an operating position, said control valve beingoperable to by-pass fluid flow from said inlet port through said bypassvalve to said discharge port while said check valves hydraulically lockthe movement of fluid in said service ports and alternatively connectingfor fluid flow said inlet port with one off said service ports andconnecting for fluid flow said discharge port with the other of saidservice ports while terminating fluid flow from said inlet port throughsaid by-pass valve to said discharge port, a control lever, and linkmeans connecting said valve plunger with said control lever and themovable work member of said fluid motor whereby said control lever issettable to move said valve plunger to an operating position forenergizing said motor for movement in a direction to return said valveplunger to a neutral position when said work member of said motor hasreached a position corresponding to the position of said control lever.

3. An hydraulic power transmitting system comprising a source of fluidflow, a fluid motor having a movable work member, a control lever, acontrol valve disposed intermediate said source of fluid flow and saidmotor, said control valve being manipulative from a neutral position toaccommodate fluid flow therethrough to energize said motor, said controlvalve being resettable to a neutral position for terminating fluid flowto said motor, a fluid pressure responsive by-pass valve having a pairof movable elements in opposed relation disposed in said control valve,said by-pass valve being operable to by-pass fluid from said source offluid flow between said elements when said control valve is in a neutralposition and alternatively terminate said fluid flow between saidelements when said control valve is in an operating position, a pair ofcheck valves disposed in said control valve, said check valves beingpositioned to prevent fluid flow from said motor when said control valveis in a neutral position, said by-pass valve elements being operable toopen selectively one of said check valves for permitting fluid flow fromsaid motor therethrough when said control valve is in an operatingposition, and link means connecting said control valve and said controllever and said work member whereby said control valve is moved from anoperating position to a neutral position when said work member reaches aposition corresponding to the position of said control lever.

References Cited in the file of this patent UNITED STATES PATENTS1,955,154 Temple Apr. 17, 1934 2,524,055 Hubert Oct. 3, 1950 2,637,259Acton May 5, 1953 2,720,755 Gardiner Oct. 18, 1955

